We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Graphics with transparent backgrounds
I'm new here, so I'm still a little clueless. Please bear with me.
My word document contains a graphic with a transparent background, could this pose a problem with printing? When I uploaded my manuscript, Lulu told me that they had to flatten the transparencies in my document, does that mean that everything is okay now, or do I need to do something else?
(I'm not sure if "flattening transparencies is the correct term, I'm using Lulu in another language, so I don't know what exactly it says in English.)